Mineral lubricating oil composition



P atenteci Oct. 5, 1954 UETED STAT ear orric-E MINERAL LUBRICATING OILCOMPOSITION No'DraWing. Application July 23, 1952,

Serial 010.300,!92

2 Claims.

Thepresent invention relates to the use of 4,4 isopropylidine bis(2isopropylphenol) as an additive for mineral lubricating oilcompositions.

Various bis phenols have been suggested as additives for organiccompositions subject to oxidation. The use of such phenols containing ahis linkage in the para position with respect to the hydroxyl radicalshas met with little success. For example, diphenylol propane isrelatively ineffective as a lubricant antioxidant. Furthermore, thiscompound cannot be used in the usual mineral lubricant compositionsbecause it is substantially completely insoluble in such materials atordinary temperatures.

In accordance with the present invention it has been found that minerallubricating oil compositions containing dissolved therein small amountsof 4,4 isopropylidine bis (2-isopropylphenol) are excellentcompositionsfor use in lubricating in- More- This compound is readilyand inexpensively prepared by condensing ortho isopropylphenol withpropionaldehyde or dimethyl ketone, usually in the presence of acondensation catalyst. The general method of preparation of suchcompounds is well known to the art and does not form a part of thepresent invention.

The 41,4 isopropylidine bis (2-isopropylphenol) is dissolved in minerallubricating oils in amounts in the range of about 0.05 to 1.5 or 2% byweight, the upper limit being restricted to some extent by the type ofmineral oil base stock being used. A preferred concentration is in therange of about 0.1 to 1.0% by weight.

The lubricating oil base stocks used in the compositions of thisinvention may be straight mineral lubricating oils or distillatesderived from paraninic, naphthenic, asphaltic or mixed base crudes. Thelubricating base stocks will generally range from about 40 to 150seconds (Say- 2 bolt) viscosity at 210 F. The viscosity'index may rangefrom about 0 to 100 or higher, al-

though for aviation lubricants, which are the preferred base stocks inthe practice of the present invention, the higher viscosity indexes arepreferred. The bisphenol of the present invention is quite suitable,however, for automotive lubricants, diesel lubricants and the like. Inaddition to "the above mentioned materials, the compositions may containother agents including pour point depressants, viscosity indeximprovers,

by reference to the following examples.

- oiliness agents and the like.

Example '1 .Solubility studies The bis phenol compound oi-thepresentinvention, lfl' isopropylidine bis (2-isopropylphenol) wasioundto be readily soluble in mineral lubricating oils to the extent of asmuch as 1.0 to

1.5 weight percent at room temperature.

Diphenylol propane, on the other hand, was insoluble in minerallubricants at room temperature. A solution was obtained when 0.25 weightpercent diphenylol propane was agitated in a mineral lubricant atatemperature of 250 F., but, on cooling to room temperature, thisbisphenol substantially completely crystallized out of solution.

Example 2.-Staeger oxidation studies Two highly solvent-extractedMid-Continent lubricant base stocks were used in these studies. Basestock I had an S. S. U. viscosity at 210 F. oi 85. Base stock II had anS. S. U. viscosity at 210 of 43 and a viscosity index of 112. Blends ofeach of these oils containing 0.25 weight percent of various bisphenolsas well as the oils per se were tested.

The test employed was a modification of the Staeger test and consistedessentially of storing a 200 ml. sample of oil in a rotating shelf ovenmaintained at 100 C. -1. A 40 x 70 mm. freshly polished copper strip wasplaced in the 400 ml. container to serve as an oxidation catalyst. Thestrip was removed every 72 hours and replaced by a clean strip. Theshelf moved at an angular velocity of 4-6 B. P. M., and positiveventilation of 1.5 to 2.0 cubic feet of air per hour was maintained. Oilsamples were withdrawn periodically from the container and theneutralization num- Staeger" Oxidation Life, Hours Additive Tested BaseBase Stock I Stock II None 75 95 Diphenylol propane 75 854,4-ispropylidene-di-o-cresol 84 220 4,4-isopropylidine bis(2-isopropylpheno1) 154 440 2,2 bis(2-hydroxy-3-tert.-butyl-5-methoxyphenyl) propane 100 285 The compoundof the present invention is about two to four times as effective as thecorresponding bisphenols containing either no alkyl substituents ormethyl substituents, It is also markedly superior to a meta bisphenolcontaining methoxy substituents.

Example 3.Aluminum cup coking studies Oil blends were preparedcontaining various concentrations of several bisphenols in asolventextracted Mid-Continent aviation base oil having a viscosity at210 F. of about 100 Saybolt seconds. These blends and a sample of thebase oil per se were evaluated by the aluminum cup coking test. Thistest determines the eifectiveness of an additive for inhibiting cokingof lubricants under the severe temperature conditions normallyencountered in aviation engines.

The test was conducted by placing the oil in an aluminum measuring cupof known weight and stirring the oil while applying heat. The side wallsof the cup were maintained at a temperature of 500 F. while heating theoil at the bottom 4 until it reached 550 F. The stirring was thenstopped for 10 minutes followed by stirring for 10 minutes. At the endof the fourth alternate stirring and non-stirring period, the oil wasdiscarded, and the cup was weighed. The results are shown in thefollowing table:

The compound of the present invention is considerably more effectivethan a related compound having a his configuration ortho to the hydroxylgroups and alkyl substituent groups in both ortho and para positions.

What is claimed is:

1. A mineral lubricating oil composition containing a major proportionof a mineral lubricat ing oil and dissolved therein a minor oxidationinhibiting amount of 4,4'-isopropylidine bis (2- isopropylphenol) 2. Acomposition as in claim 1 wherein the amount of said bis phenol is inthe range of about 0.05 to 1.5% by weight, based on the totalcomposition.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,017,827 Bannister Oct. 5, 1935 2,295,985 Baird Sept. 17,1942 2,482,748 Dietzler Sept. 27, 1949 2,515,906 Stevens July 18, 19502,591,651 Young Apr. 1, 1952 2,636,002 Capell Apr. 21, 1953 2,651,572Bichon" Sept. 8, 1953

1. A MINERAL LUBRICATING OIL COMPOSITION CONTAINING A MAJOR PROPORTIONOF A MINERAL LUBRICATING OIL AND DISSOLVED THEREIN A MINOR OXIDATIONINHIBITING AMOUNT 4,4''-ISOPROPYLIDINE BIS (2ISOPROPYLPHENOL).